Electron cyclotron resonance plasma deposition process and device for single-wall carbon nanotubes and nanotubes thus obtained

Abstract

Electron cyclotron resonance plasma deposition process and device for single-wall carbon nanotubes (SWNTs) on a catalyst-free substrate, by injection of microwave power into a deposition chamber comprising a magnetic confinement structure with a magnetic mirror, and at least one electron cyclotron resonance area inside or at the border of the deposition chamber and facing the substrate, whereby dissociation and/or ionization of a gas containing carbon is caused, at a pressure of less than 10 −3 mbars, in the magnetic mirror at the center of the deposition chamber, producing species that will be deposited on said heated substrate. The substrate surface includes raised and/or lowered reliefs. The invention concerns the SWNTs thus obtained.

1. Electron cyclotron resonance (ECR) plasma deposition process for single-wall carbon nanotubes (SWNTs) comprising the following steps:
 providing a catalyst-free substrate, which surface includes raised and/or lowered reliefs, in a deposition chamber; 
 heating the substrate; 
 injecting microwave power in the deposition chamber, the deposition chamber comprising a magnetic confinement structure with a magnetic mirror, and at least one ECR area inside or at the border of said deposition chamber and facing said substrate, thereby causing dissociation and/or ionization of a gas containing carbon, at a pressure of less than 10 −3  mbars, in said magnetic mirror at the center of the deposition chamber, thereby producing species that will be deposited on said heated substrate; and 
 depositing SWNTs on the catalyst-free substrate. 
 
     
     
       2. Process according to  claim 1 , in which the raised and/or lowered reliefs comprise at least one surface approximately perpendicular to the main plane of the substrate surface. 
     
     
       3. Process for deposition according to  claim 1 , comprising the following steps:
 heating the substrate; 
 creating a pressure of less than or equal to 10 −3  mbars, of a gas containing carbon; 
 injection of the microwave power and creation of the plasma from said gas containing carbon, for a value of the magnetic field corresponding to electron cyclotron resonance; 
 creation of a potential difference between the plasma and the substrate; 
 dissociation and/or ionization of molecules in said magnetic mirror at the center of the deposition chamber; and 
 deposition of the formed species on said substrate to obtain single-wall carbon nanotubes. 
 
     
     
       4. Process according to  claim 1 , wherein the magnetic mirror is unbalanced. 
     
     
       5. Process according to  claim 1 , wherein the magnetic mirror is such that the magnetic field is maximum (B max ) at the microwave injection, and the magnetic field is then minimum (B min ) at the center of the deposition chamber, and finally the magnetic field raises again on the substrate (B substrate ). 
     
     
       6. Process according to  claim 1 , wherein the input side mirror ratio at the microwave injection, and as defined by r 1 =B max  (in Gauss)/B min  (in Gauss), is greater than (or equal to) 4. 
     
     
       7. Process according to  claim 1 , wherein the mirror ratio on the output side, towards the substrate, defined as Y 2 =B substrate  (in Gauss)/B min  (in Gauss), is greater than or equal to 1.5. 
     
     
       8. Process according to  claim 1 , wherein the substrate is heated to a temperature of 500° C. to 700° C. 
     
     
       9. Process according to  claim 1 , wherein the substrate is heated by electronic bombardment and/or external heating. 
     
     
       10. Process according to  claim 1 , wherein the substrate is positively polarized and the plasma is grounded. 
     
     
       11. Process according to  claim 10 , wherein the substrate is polarized at between +20 volts and +100 volts. 
     
     
       12. Process according to  claim 1 , wherein the plasma is negatively polarized and the substrate is grounded. 
     
     
       13. Process according to  claim 12 , wherein the plasma is polarized at between −20 volts and −100 volts. 
     
     
       14. Process according to  claim 1 , wherein the surface of the substrate includes trenches and/or gouges and/or grooves and/or ridges and/or corrugations and/or holes and/or cavities and/or pads and/or spikes and/or projections and/or bumps and/or embossments. 
     
     
       15. Process according to  claim 1 , wherein the substrate comprises tungsten. 
     
     
       16. Process according to  claim 15 , wherein the substrate is chosen from solid tungsten substrates including a layer of tungsten deposited on silicon or glass, and substrates including a tungsten grid.